Conventionally, in an image forming apparatus that forms an image on a long-size medium (hereafter, also called “long medium”) such as a rolled sheet of paper, not only a print process but also a process to cut the medium is performed. Then, in an image forming apparatus supporting a conventional long medium, in order to detect a cut position or a print start position, alignment references such as black color marks (hereafter, also called “black marks”) displayed on the long medium and the edges of labels formed on the long medium are determined. In an image forming apparatus supporting a conventional long medium, the positions of such alignment references as mentioned above are detected using an optical sensor (for example, a reflection sensor or a transmission sensor).
As an image forming apparatus supporting a conventional long medium, for example, there is an apparatus according to Patent Document 1. In the image forming apparatus according to Patent Document 1, when using a long medium where labels are temporarily attached to a long shape base sheet, the outer shapes of the labels are detected using a transmission sensor. Also, in the image forming apparatus according to Patent Document 1, when using a long medium where black marks are printed with constant gaps, the black marks are detected using a reflection sensor.